Dramatic changes in the dissolved 230Th concentration of seawater in Canada Basin between 1995 and 2009: a transient Arctic circulation signal?
Bibliographic record
Abstract
A dissolved 230Th profile measured in the Arctic Ocean in 1983 under permanent ice cover (Alpha Ridge; 85°50’N, 108°50’W) documented concentrations substantially higher than in any other ocean basins, reflecting very low particle flux and scavenging intensity (Bacon et al., 1989). In contrast, similar measurements closer to the ice edge conducted in Canada Basin in 1995 (72°32’N, 143°50’W, 3500 m) found much lower concentrations, reflecting higher rates of particle flux and particle scavenging (Edmonds et al, 1998). In November 2007, we measured dissolved 230Th at two Canada Basin stations (KC2000; 71°44’N, 135°30’W, 1925m; KC2700; 72°28’N, 136°56’W, 2490m) and compared these profiles to that obtained in 1995. While the earlier 230Th profile displayed a linear increase in concentration with depth, as predicted by a simple reversible absorption model which neglects water mass transport, the 2007 profile obtained at KC2700 documented very large deviations from linearity, with a prominent maximum centered within the Atlantic Water. The profile taken closer to the shelf (KC2000) did not show this feature. These observations suggested that the prominent maximum in 230Th concentration at KC2700 could have been produced by entrainment of water from the permanently ice-covered Arctic interior into the warm Atlantic Water which is slowly penetrating into the eastern sector of Canada Basin and as such could provide information on the path of Atlantic Water intrusion. New data obtained from the same area in September 2009 during the Canadian IPY-GEOTRACES program documents the evolution of this signal.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".